I have watched my mom have sex with other men.

I have been wanting to get this off my chest so I made this throwaway account. I've never told anyone about this, I thought that maybe doing this anonymously on the Internet would be the best. I'm 17 years old and I live with my mom. I stayed with her after she and my dad got divorced. I still keep contact with my dad and I visit him pretty often. Well because my mom is not married anymore, ever since her and my dad got divorced she has been bringing guys to the house. She introduced one of them to me and said that he was her "friend"from work. His name is Mark and he comes over pretty often. When he comes over, if I'm in the living room, I just go to my room. My mom makes him food and then they go to my mom's room. They put on music and then minutes later I can hear my mom screaming. Well yeah I know they sex. I guess they think that I can't hear them over the music, but it can almost be heard across the whole house. Our neighborhood is pretty quiet, there are no cars passing by in front or anything. I've sneaked around the back and watched them have sex through a corner of the blinds. I know I shouldn't do it, but curiosity got the best of me. I've doing it for about a year now. This is also how I found out that she's been having sex with three different guys. She's never introduced to the other two. When the other two guys come over, she goes outside, tells me to go do my homework, and then takes them into her room. I've watched her have sex with them two. I don't why she would even think that I cannot hear her screams. Every time they come over, it's the same thing. I'm 17 years old, I know what the sound of sex is. I don't know what I should do because she is not married to my dad anymore and she is an adult. This is why I've never told her anything, and it's also embarrassing. I can't picture myself telling her that I hear her screaming every time her boyfriends come over and I know that they are obviously having sex. I'm also very conflicted about telling her because I will admit that every time I watch her have sex with them I get a huge adrenaline rush because I know it's not right to be watching and even less when it's my mom with other guys that I don't even know. I don't know, I might be addicted or I'm not sure, because everytime I hear them walk in I start getting aroused because I know what is gonna happen. This has been messing with my head for a long time and I don't know what to do. I know, I know this is not normal and I shouldn't do it but I also kind of don't want it to end. I hope you guys can give me some advice. I know sex is nothing bad and she is an adult and can do whatever she wants. She's not hurting me or anything, she's just doing what normal adults do. I'm kind of okay with it but at the same time and I know it's not right to be watching your mom have sex. Should I tell her about? And if yes, how do I tell her?